A new study in India says that 71% of farmers who tried out a genetically modified pest-resistant variety of cotton suffered an average decrease in crop yield of 35%, compared with farms where traditional coton was grown.

The study says it also found that the new variety failed to live up to claims that it needed significantly less pesticide treatment, and that its cultivation was cheaper.

However, a spokesman for Monsanto, the biotech company which introduced the new cotton seeds, disputed the study's findings, and said that the lower yield could be due to drought.